Cleaning cupreous articles



Patented Sept. 2, 1,952

- UNITED STAT es msm-gomez oL'ENlNG CUrnEoUs ARTICLES Clermont J. Snyder and Willis G.`MacLe1Iand, VHastings on Hudson, N. Y., assi'g'nors to Anaconda Wire and Cable Company, a corporation of 'Delaware y, "No Drawing. Application May 22, 1948,

e, `Serial No. 28,748

This intention relates to removing scale'froin cupreous articles by heating'su'ch articles in a' halogen-bearing atmosphere and subsequently cooling them. Heretofo're it has been necessary" to introduce the halogen'into,the'atmosphere by volatilizing aimetal halide, 'as only indifferent results have been,A attainedfby introducingr an elemental halogen or halogen acid directly into such atmosphere. We have now discovered kthat elemental halogens and halog'enacids yield very satisfactory v results when the atmosphere in which thefarticles areheated is substantially free of fuel combustion products, 'and the present invention isvpr'edicated on this discovery.

"United VStates Patents Nos. 2,291,201 and 2,291,202 to W. n. Bassett, JMC. J. snyoerand W. G. MacLellanddes'ci-ibe processes fior cleaning lcupreo'us articles by" halogen treatment, thereby toremove they oxide scale thatk is always present on such hot-Worked shapes' ja's hot-rolled copper frofds from which .Wire is 'drawnl The process of Patent No. 2,291,201,involves` heating the cupreous article in afurnace 'atmosphere' containing `the vapor of Va volatilizable n'i'etal halide', and thereaftercooling the "article, preferably `by quenching' in water; `The process of Patent No. 2,291,202 involves iirstdippi'n'g the' article in `an aqueous solution of a chloride, then heating the article in a furnace, 'and iinally cooling the article, as by quenching." vThe" process of 'c th'e latter patent has been successful with hydrochloric acid as thesolution in which the article is first dippedthereby causing initial 'reaction of the acid with the article to take place in aqueous' solution. Heretofore, however, it has 'not been feasible to `use hydrochloric 'acid inth'e process of the 'former patent, by introducing it" in gaseous form direcuy into the' atmosphere in which niej article is heated, because very, unsatisfactory'hresuits have `been attained by so doing. 'ljhe processes of both of these patents Ihave been used successfully, but that of Patent No. 2,291,201 has commercial advantages. because no' preliminary dipping 'of' the article to be cleaned a.

' Wenave foonfurnace vin which the veupreous 4article .is treated;

provided such atmosphere "is substantially fre `egcf,. fuel combustion products by.. .f ffuel combustion pro'ductshwe mean the usualgaseous combustion,

products of ordinary carbonaeeous` and hydrothat demented .halogne and 'aygbejsed in piace of 'th ivia-J l tiiizabie in-etai' "hannes.dejscrbed'in Patent .Ne-.L 2,291,201, for the purpose off'establishingan efec'fveV halgh-beang atriisjpilre Within the volaille. (c1. 1314-43 )4 carbon fuels resulting' from burning such 4fuels. air). Moreover, 'vvha've found that'the use oir these substances has distinct advantages that do not ensue from the use of a volatilizable metal halide. One such advantage is fthatvvhen'an elemental halogen or halogen acid is used, the article in'ay be heated more rapidly and its treatment maybe completed sooner'than with metal halide vapors. i Another advantage is that batchtype treatment of a Weigllied4 amount ofthe articles lwith afmeasuledamount of the halogen or halogen acid isp'ossib-le, resulting in closer controlover the duality of 'the cleaning' treat- I'I'Ielt.N A l f jlnffgeneral, theniesent inethod'for cleaning' cul'pr'eo'us articles is `sin'iila'ito that described in Patent No. v2,291,201 and involves introducing the article 'to be vcleaned,.While it is substantially halogen-free, into a Vhalogen-bearing atmosnhere` heating` it therein to a temperature of about 1250 andsubseq'uently cooling it. In

accordance `vvith 'the present invention, however, i

the atmosphere inwvh'ich the article is heated is maintained substantially free from fuel 'combustion products, and the halogen is introduced intosaid'atmos'phre by supplying directly thereto anjdn gaseous form asubstance ofthe group co'isisting of elemental lhalogens and vhalogen ac s. j j

Whienfthe halogen contentof the atmosphere is v"provided Vby vapor from a* Volatilizable metal halide asdsoribed in Patent No. 2,291,201., most effective cleaning is accomplished by heating the article at `the rate of about 50 Eber minute from roomtemerature to about 700 F., so that the article f is held for a total'tirne of tvvelve to fifteen minutes' at aternperaturebelow 700 F. The need for initial heatingat this rather loW rate evidently is required to .allow for 'some of the vapor4 to collect 'on the article and react initially with its oxide scale, and with metal halide vapor such reaction appears to occur most leffectively at a temperature-inthe range from 500 F. toY 700 We have found that When an elemental halogen or halogen acid is used in `place oi Ia volatil'izable metal 4halide to supply the halogen content of the Vtreatiner'it atirlos'pher'e, the time of heating at a temperature belowy 700 F. need be only two to ye minutes,V and such heatingv may be 4at a considerably lovvertemperature--down to 300 Vlil. Y,

Qonseduently, ten minutes or so may be saved 1n the tirneyrequired for treating the article, and furnace equipment of givenfsi'zecan be marde to handle a corresnondinglylgreater amount of cubreous articles per day.

We believe the reason Why the use of elemental halogens and halogen acids permits of more rapid treatment than the use of volatilizable metal halides is that these substances are highly reactive at temperatures much lower than that at which most metal halides yield substantial quantities of vapor. When the halogen is supplied as a metal halide vapor, an appreciable length of time is required for an effective amount of it to accumulate on the article and to undergo the reaction that initially takes place, but when an elemental halogen or halogen acid is employed, such reaction takes place so rapidly that a prolonged period of heating is not necessary. As stated above, however, it is necessary that the atmosphere in which. treatment With an elemental halogen or halogen acid is carried out be substantially free of fuel combustion products.

If the cupreous article is heated in a direct ,fuelfired atmosphere, very unsatisfactory results are obtained by using an elemental halogen or halogen acid, although, for somereason that we are unable to account for with certainty, metalhalide vapors are effective even in the presence of "fuel combustion gases.

Another advantage found to resultfrom the use of elemental halogens and halogen acids in lieu of volatilizable metal halides is that batch-type cleaningoperations can be employed,v

using a measured amount of the lhalogen or halogen acid to treat a `known weight of cupreous articles. When a volatilizable metal halide is employed, it is not feasible to measure the amount of metal halide vapor that is used to treat any' given quantity of articles. Consequently, closer control over the cleaning operation is possible by using an elemental halogen orfhalogen acid in accordance with the present invention than when a volatilizable metal halide is employed.

The elemental halogen or halogen Vacid isv introducedA in gaseous form into the ,atmosphere in which the cupreous `article is treated. The halogens. that are n ot normally gaseous (bromine'and iodine), and halogen acids that are used in aqueous solution, are rendered gaseous by vaporizing them, and the vapor is introduced into the treatmentatmosphere. Vaporization may be accomplished outside the oven or furnace in which treatment takes place, and the vapors may then be led into the oven or furnace;1or a measured quantity of the substance may be introduced directly into the furnace and may there be vaporized into the treatment atmosphere.

Following are examples of ways in which the method of the invention may be carriedout:

Example 1.-A known weight of hot-rolled copper rods, having a scale composed mainly of cuprous and cupric oxides, is introduced into an electrically heated vrnuiTle-type furnace, and therein is heated as rapidly as the furnace. permits to a temperature of about 1250 F. During at least the initial part of this heating.' before the rods have attained a temperature of 700 F., a small stream of chlorine gas is flowed into the furnace atmosphere. The rate of flow of thechlorine, and the length of time forv which it ows, are correlated with the amount of rods being treated to convert at least 1%, and 'preferably from 1% to 2%, by weight of the rods to an easily removed scale (scale formation to this extent has been found desirable for joptimum cleaning).

ing operation, but it is preferable "to introduce The'ow of chlorine,V may becon-V tinued throughout the entire period `of the heat-' it all, or nearly all, during the period that the rods are below 700 F. After the rods have reached a temperature of 1250 F., they are removed from the furnace and cooled to room temperature. Cooling may be in any manner desired, as pointed out in Patent No. 2,291,201, but generally it is convenient and most satisfactory to quench the rods in water. When the rods have cooled, a flaky scale peels readily and completely from them, leaving a clean unoxidized metal surface of excellent quality for wiredrawing.

Example 2.-A charge of hot-rolled copper rods, of known weight, is introduced with a measured quantity of iodine crystals into an oven heated to a temperature in the range from 300 F. to 700 F. The iodine quickly vaporizes at this temperature. The oven may be heated electrically, o1' may be indirectly heated by a fuel flame, but in any event the oven atmosphere is free of fuel combustion gases. The rods are held in the heated oven atmosphere for two to ve minutes, but it is not necessary that they become heated to the oven temperature. After two to ve minutes in the oven they are' transferredv to a' furnace in which they are heated rapidly to a final temperature of about 1250 F. The furnace may be entirely separate from the oven, or oven and furnace may be two parts of the Y same heating apparatus, arranged so that lthe rods may be transferred from one part to the other easily and quickly. The transfer to the furnace may be made immediately after the oven treatment, 'or the rods may be stored in the air and allowed to cool to room temperature after the oven treatment and before being transferred.

to the: furnace.' The furnace atmosphere may be free of iodine vapor or other halogen during the latter period of heating to 1250 F., and may 5 contain substantial quantities of fuel combustion gases, as' the'preliminary loven treatment at temperatures below 700 F. has resulted in effective accumulation'of iodine or other halogen on the rod surfaces and has caused theinitial reaction to occur. After attaining a temperature of about 1250 F., the rods are withdrawn from the furnace and cooled as by quenching.

Each of the preceding examples is based on batch-type operation, in which a known weight.

of rods is treated with a measured quantity of halogen or halogen acid. As previously stated.

provided the design of the furnace is such as to exclude fuel combustion gases from the atmosphere in which the'copper'rodsor other cupreous articles are treated. Such a substitution results in making the process more rapid, aspreviously mentioned herein. If a continuoustype furnace is employed, and if .a temperature gradient '.is

maintained in the furnace 'as described'in Patentv No. 2,291,201, it is generally preferable to introduce the 1 halogen or halogen acid'in gaseous form into the cold end of the furnace,l rathery than into the hot end as is done with the'metal halide;V The elemental halogens and halogenv acidsreact with the copper of the articles rapidly enough'V at alijlatively'lo'w temperature sontha-'t'v Itis,

it.v `not. necessary-l for.::these substanceseto: be; brought incontact with therods at the temperature `,of .thelfurnace H'Indeed, it yis neces# sary, that :at least some: preliminary lreaction take. place bietwecuthe halogen and.' halogenaacidand the rod 'or other article. before th-eilatter .has beenheated to abovefOu? 1. f l Following `is :abriefzsummary of* the 'formsin which some of'. the halogens andvhalogen acids have .been vused in accordance withwtheiinvention,:. and `an `indication :of the resultsf obtained.. In each case hot-rolled copper rods, .black 'on' accountcfthe presence of anfouter scaleof cupricioxidewere the. articles being treated.VVV L TheV initiallyv cold rods were. heated inV a munie-type furnace to a final temperature near *125095 F., and thenl were quenchedin` water. Heatingfwas accomplished as rapidly as the furnace` would permit, the temperature` of thefurnace atmospherebeingaboutlSOOfF' i (a)4 Chlorine! gas* was flowed into the Vfurnace during the first iive minutes of the hea-ting cycle; v

about at the rate-of one-half liter (at normal temperature and pressure) per minute -per hundred pounds of rods. A very heavyscalewas formedbult-the-results were goed. i Y

`(b.) Chlorine gas was owedin' at the same ratei as in- (a) but for only the-first threeminutes of `theheating cycle, with excellent-results. i (c) Chlorine gasY was flowed-infcontinuously ifi About 10Q cubic centimeters -of substan-` tially saturated Vbronfiine fwater vper"hun`d red pounds or rods was introduced with the rod'sjinto the furnace. @roodv cleaning was obtained:V

(g) A slow stream of` hydrochloric acid gas wasl flowedinto thefurnaceV during the initial part-ofthe heating cycle. Good cleaning resulted.

(h) About 2 cubic centimeters .of aqueous hydrobromic acid per hundred pounds of rods was introduced'into theV furnace along with the rods. Very good results were obtained.

(i) Approximately `cubic centimeters of vaqueous perchloric acid solution per hundred pounds of rods was introduced with them, into the-furnace; Good cleaning of the rods followed. (This reagent must be 'used with care; as it is @XrlQSii/.QJ f, (i) Aboutl grams ofchlorosulphoniciacid per hundred pounds of rods was introduced into the furnace with the rods. A very heavy scale formed, indicating that considerably more chlorosulphonic acid than was necessary had been used, but the cleaning of the rods was excellent. The adverse effect of fuel combustion products on the course of the cleaning operation is evident from a number of tests. For example, in one test chlorine gas was introduced in the same manner as in paragraph (c) above, but in admixture with commercial city gas and an excess of air. 'Ihe city gas burned as it entered the furnace with a blue flame, owing to the excess of oxygen. Under these conditions only a moderate and rather unsatisfactory degree of cleaning was obtained. In another similar test in Good results lwere- 6 which an insufficient amount, of air toburn all of the city gas, .was used, so ,that the. fuel burned with a; yellow flame',- no' 1 cleaning y resulted'. 1 viden'tlythe moderateV cleaning 'in the first of these two 1: tests: 'was i. made possible by the 'dilution "of the'. combustion ff'gases, .by fthe: excess. air,laridl by thezpresence'ofwthe roxygenfiof" the excess When: this: excessY ofuair'r was eliminated! So thatv the combustion gases were.V` relatively concentratedin the furnace,v theucleaning action stopped. Similar: results, were `obtainl'ed when theprexnixed city gas and air were introduced yand burned within Vthe vfurnace separately from the chlorine. When a'siiaine ofburn-in'g'! city gas and airfwas' introduced ntol'the E11-mace While' treating 5015156? rods. therein with iodine "introduced with the rods. in the 'form iofr" iodine crystals, the 'amount off scale: formo and' subsequently separated from the: rods vvas""too f small-1 to result iii-thorough cleaning. if I l The introduction of'air `into the furnace along with thehalogen or lhalogen aeidi's advantageous rather: than otherwise.- f ThusV withchlorinefor example, better cleaning" was accomplished when the chlorine is introduced in astreaiir of" air, tha'ni when thefurnace is fairlytightly closed and commercially pure chlorine` alone is]l introe duced into the furnace The easilyi separated scale; that forms asar result ,ofV the' vtreatmentv i seeinstorbeA an oxyhali'd'e, and evidently its' ,for-'j'v mation is:V favored by the presence off free oxygenin'ad'ditien to the combined "oxygerr presentin the tightly adhering initial scalefoffcuprous andy cupric oxideslil 1" l A f It' isei'fidentjfromv the data given above'- that` only quite' f small-- quantitiesc'f'halogens and fial-v ogen acids are required tofproduce goed clean-"f` ing.` Indeed, toolar'ge a quantity of any ofthesesubstances should be avoided in ordertopre*- vent an excessive-lbssof metall in the scaleziln the case'ofblackr hot-rolled copper rods'vfor wiredrawing-(whi'ch are vgenerallyabout 1%, inch inY diameter and' have Lalueavy coating of' cuprousv and cupricoxides) the amount of l'scaleremoved shoul'dlbe from 1%'fto `24% of theweight'of the'y rods'.AV Atleast about 1%'fby weight of therod'si must bel-removedI to' heL Sure ofco'mpl'ete' clean?,

ing*andipreferably'theiambuntis about 1.5% fr` optimumv results.. From 2 to! 20,' grams]l of Jtlie.

halogen,` or halogen: acidlper hundred` poundsof"4 cupreous articles is. generallyv enough to form this amount of .readily removed! scale, when'Y the: articles are` black hotfrolledcopper rods. Larger` or srnaJlejr amounts. ofltliese. substances, and a. larger forv js'm`a".ller`v ifzercentage` ofr metal-lostdn-thescale` will, however, vbepreferable when the ar.-V ticle' being treated hasl arr appreciably' differentir ratio of.- surface-to-volume than ordinary 4hot-f:

rolled 'copper rods for wire-drawing.

We claim:

1. In a process for removing scale from a cupreous article involving heating the article in a halogen-bearing atmosphere and subsequently cooling the article, whereby scale separates readily therefrom, the improvement which comprises introducing the article while substantially halogen-free into an atmosphere that is substantially free from fuel combustion products and from metal halide vapors, introducing a halogen into said atmosphere by supplying directly thereto and in gaseous form a substance of the group consisting of elemental halogens and halogen acids, and heating the article in said atmosphere to a temperature of about 1250 F.

2. In a process for removing scale from a cu- Dreous. article involving heating the article ina chlorine-bearing atmosphere and subsequently cooling the article, whereby scale separates readily therefrom, the improvement which comprises introducing the articlewhile substantially halogen-free into an atmosphere that is substantially free from` fuel combustion products and from metalfhalide vapors, heating the article in saidV atmosphere to a temperature of about 1250 F., and introducing chlorine gas directly into said atmosphere at least during the initial stages of said heating.

3; In a process for removing scale from a cupreous article involvingheating the article in a halogen-bearing atmosphere and subsequently cooling the article, whereby scale separates readily therefrom, the improvement which comprises introducing a kbatch of known weight of said articles into a furnace and rapidly heating the batch therein in an atmosphere substantially freeof fuel combustion products and of metal halide vapors at least to a temperature in the rangefrom 300 F. toY 700 F., introducing into said atmosphere during such heating a substance ofl the group consisting of -elemental halogens and halogen acids, said substance being supplied injgaseous form directly to the atmosphere in which the batch of articles is heated and being measured infamount relative to -the weight of the y batch of articles to yield at least about 1% of said weight of easily separated scale, and thereafter further heating the batch to about 1250 F. andthen cooling it.l

' 4. In a process for removing scale from a cupreousarticle involving heating the article in a chlorine-bearing atmosphere and subsequently cooling the article, whereby scale separates readily therefrom, the improvement which comprises introducingv a batch of known weight of said articles into a furnace and rapidly heating the batch therein in an atmosphere substantially free of fuel combustion products and of metal halide vapors at least to a temperature in the range from 300 F. to 700 F., introducing chlorine gas directly into said atmosphere during such heating, the amount of chlorine I`gas being measured in amount relative to the weight of the batch. to yield an amount of easily separated scale yequal to at least about 1% of said weight, and thereafter further heating the batch of articles to about 1250 F. and then cooling it.

5. In a process for removing scale from hotrolled copper rods involving heating the rods in a chlorine-bearing n atmosphere and subsequently cooling them,wwhereby scale separatesreadily therefrom, the improvement which comprises in troducing a weighted batch of rods into a furnace andrapidly heating the batch thereinv in an atmosphere substantially free of fuel combustion products and of metalhalide vapors at least to a temperature in the range from 300 F. to '100 F., flowing. a small 'stream of chlorine gasinto said atmosphere during at least a part of the time of such heating, the rate of flow lof the chlorine gas stream and the time 'of said ow being such as to introduce into the furnace atmosphere an amount of chlorine sufficient to convert from 1% to V2% by weight of the batch of rods to the form of easily removed scale, and thereafter further heating the rods to about 1250 F. and then cooling them.

6. In a process for removing scale from a cupreous article involving heating the article -in a halogen-bearing atmosphere and subsequently coolingthe article, whereby the scale separates readily therefrom, the improvement which comprises introducing the article into an oven and heating it therein in an atmosphere substantially free of fuel combustion products and of metal halide vapors at a temperature in the range from 300 F. to 700 F., introducing into the oven atmosphere during such heating a substance of the group consisting of elemental halogens and halogen acids, said substance being supplied in gaseous form directly to the oven atmosphere, transferring the article after such heating to a furnace and heating it therein to a temperature of about 1250 F., and then removing the article from the furnace and cooling it.

7. In a process for removing scale from a cupreous article involving heating the article in ,a chlorine-bearing atmosphere and subsequently cooling the article, whereby the scale separates readily therefrom, the improvement which com,- prises introducing the article into an oven and heating it therein in an atmosphere substantially free of fuel combustion products and of metal halide vapors at a temperature in the range from 300" F. to 700 F., introducing chlorine gas directly into the oven atmosphere during such heating, transferring the article after such heating to a furnace and heating it therein tota temperature of about 12 50 F., and then removing the article from the furnace and cooling it.

VcLERr/rorrr J. SNYDER. WILLIS G. MACLELMND.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS lBassett July 28, 1942 

1. IN A PROCESS FOR REMOVING SCALE FROM A CUPREOUS ARTICLE INVOLVING HEATING THE ARTICLE IN A HALOGEN-BEARING ATMOSPHERE AND SUBSEQUENTLY COOLING THE ARTICLE, WHEREBY SCALE SEPARATES READILY THEREFROM, THE IMPROVEMENT WHICH COMPRISES INTRODUCING THE ARTICLE WHILE SUBSTANTIALLY HALOGEN-FREE INTTO AN ATMOSPHERE THAT IS SUBSTANTIALLY FREE FROM FUEL COMBUSTION PRODUCTS AND FROM METAL HALIDE VAPORS, INTRODUCING A HALOGEN INTO SAID ATMOSPHERE BY SUPPLYING DIRECTTLY THERETO AND IN GASEOUS FORM A SUBSTANCE OF THE GROUP CONSISTING OF ELEMENTAL HALOGENS AND HALOGEN ACIDS, AND HEATING THE ARTICLE IN SAID ATMOSPHERE TO A TEMPERATURE OF ABOUT 1250* F. 